Method of coating employing anionic wax emulsions

ABSTRACT

A METHOD FOR COATING A SURFACE IS PROVIDED WHICH COMPRISES CONTACTING SURFACES WITH AN ANIONIC WAX EMULSION; AND THEREAFTER CONTACTING THE WAX EMULSION DEPOSITED ON THE SURFACE WITH A CATIONIC COUPLING AGENT COMPRISING A SALT OF A COMPLEX AMINE POLYMER WHEREBY THE WAX PARTICLES IN THE EMULSION ARE PRECIPITATED ONTO THE SURFACE. ARTICLES OF MANUFACTURE HAVING SURFACES COATED BY THE ABOVE-DEFINED METHOD ARE ALSO PROVIDED.

United States Patent METHOD OF COATING EMPLOYING ANIONIC WAX EMULSIONSCraig C. Campbell, Cherry Hill, N.J., assignor to Mobil Oil CorporationNo Drawing. Filed Nov. 17, 1970, Ser. No. 90,483

Int. Cl. B44d 1/092 US. Cl. 11756 11 Claims ABSTRACT OF THE DISCLOSURE Amethod for coating a surface is provided which comprises contactingsurfaces with an anionic Wax emulsion; and thereafter contacting the waxemulsion deposited on the surface with a cationic coupling agentcomprising a salt of a complex amine polymer whereby the wax particlesin the emulsion are precipitated onto the surface. Articles ofmanufacture having surfaces coated by the above-defined method are alsoprovided.

BACKGROUND OF THE INVENTION 1) Field of the invention This inventionrelates to a method for applying a coating and, in one of its aspects,relates more particularly to an improved method for applying waxparticles onto a surface. Still more particularly, in this aspect, theinvention relates to an improved method for the deposition of waxparticles from anionic wax emulsions onto various surfaces, includingarticles of manufacture, plant surfaces and other forms of vegetation.

(2) Description of the prior art Prior to the present invention, inorder to precipitate and deposit wax particles, contained in anionic waxemulsions, in the form of external coatings or as internal sizingagents, onto various surfaces, it has been necessary to incorporate insuch formulations rosin and alum, whose function was to act asprecipitating agents. In addition, the presence of rosin and alum hasnot resulted in a neutral system. The importance of having a neutralsystem for deposition of wax particles is apparent from the fact that,for example, in the manufacture of coated cellulosic materials, such aspaper, a neutral system makes possible improved paper gaging properties,reduction in corrosion of machinery parts, reduction in efiluentdisposal problems and reduction or complete elimination of expensiveoptical whiteners. Hence, it is highly desirable to replace the rosinand alum components with a single substitnent and which would alsoprovide a neutral system with all of the attendant economic andpractical advantages.

SUMMARY OF THE INVENTION It has now been found, as more fullyhereinafter discussed, that surfaces can be effectively and economicallycoated with wax particles, by contacting these surfaces with an anionicwax emulsion, and thereafter contacting the wax emulsion deposited onthe surface with a cationic coupling agent, comprising a salt of acomplex amine polymer, whereby wax particles in the emulsion areprecipitated onto the surface.

The use of the cationic coupling agent, in this manner, makes possiblethe replacement in whole, or in part, of the heretofore employed rosinand alum as precipitating agents, thereby resulting in a neutral systemand affording all of the aforementioned advantages.

The sequence of first applying the anionic wax emulsion to the desiredsurface, followed by application of the cationic coupling agent,represents a critical condition of the coating procedure. Thus, it hasbeen found that if the wax emulsion and coupling agent are pre-mixed andthe resulting mixture applied to the desired surface, there is obtainedimmediate and total precipitation of wax particles, resulting in theformation of undesirable globs and uneven wax deposits. On the otherhand, in following the procedure in accordance with the improved methodof the present invention, an even wax precipitation and distributionover the desired surface is obtained. In this respect, 'in accordancewith one modification of the invention, the desired surface can beinitially coated with a minor amount of the coupling agent and,thereafter, following contact of the thus-treated surface with the waxemulsion, the latter is then contacted with the remaining portion of thecoupling agent. Such procedure can be successfully employed forfacilitating attraction of the wax emulsion to the desired surface.

In carrying out the coating procedure any conventional anionic waxemulsion may beemployed, from which wax particles are capable of beingprecipitated, and therefore may include wide varieties of anionic waxemulsions, well-known to those skilled in the art. Insofar as thesurface to be coated is concerned, the deposition of the wax coating maybe applied to any surface which is either anionic or cationic in natureand therefore may comprise a wide variety of articles of manufacture,plant surfaces and other forms of vegetation, including paper pulp,cotton cloth, wet process hardboard, wood and other forms of cellulosicmaterials.

Of special importance in carrying out the coating procedure of thepresent invention is the use of a cationic coupling agent. Morespecifically, this agent comprises a salt of a complex amine polymerwhich is capable of precipitating the wax particles of the emulsion ontothe desired surface. Typical examples of these salts include polyaminesalts obtained by reacting a reduced polyacrylam'ide with a fatty acid,such as formic, acetic, propionic and higher acids. Also exemplary ofthese salts are those obtained by the reaction of N-alkyl trimethylenediamines containing alkyl groups having at least 14 carbon atoms, withthe aforementioned fatty acids.

The quantity of coupling agent employed is, preferably, that amountrequired for effecting precipitation of the desired amount of waxparticles from the emulsion. For most purposes, the coupling agent iselfectively em ployed in an amount from about 0.1 to about 30% and,preferably, from about 1 to about 5%, by weight, of the weight of thewax emulsion solids.

DESCRIPTION OF SPECIFIC EMBODIMENTS The following examples andcomparative data will serve to illustrate the novel method of thepresent invention for the coating of surfaces with anionic wax emulsionsand the important results realized therefrom.

Preparation of pulp slurry A 3% pulp slurry was prepared by (1) adding60 grams of bleached sulphite pulp into 2 liters of distilled water andallowing the pulp to soak for a period of about 18 hours. The pulp wasthen disintegrated by employing Mixing of additives 222 ml. of pulpslurry was taken from the heater and placed into a 800 ml. beaker sothat slow stirring (approximately 60 r.p.m.) could be maintained. Thefiber solution was used as taken directly from the beater at thedetermined O.9% fiber solids ,(i.e., 1.96 grams of net pulp in 222 ml.)

Wax emulsion addition 1.4 ml. of anionic wax emulsion solution (based onwax emulsion volume) was added slowly by pipette with continuousstirring. The slurry thus contained 0.014 gram of wax solids (0.71% at1.96 grams of net fiber weight). The solution was then stirred for aperiod of 6 minutes.

Rosin addition 2.5 ml. (2.5 ml. of a fresh 1.0% rosin solution) wasslowly added by pipette with continuous stirring. The slurry thuscontained 0.25 gram of rosin solids (1.3% based on 1.96 grams of netfiber weight). The solution was stirred for a period of 6.5 minutes.

Alum addition 0.39 ml. of a fresh alum solution,

A12(SO4)3' was added slowly by pipette with continuous stirring. Theslurry thus contained 0.39 gram of alum (2% alum based on 1.96 grams ofnet fiber weight). The solution was stirred for a period of 6.5 minutes.

Preparation of handsheet The above-described 222 ml. of pulp solutionwith additives was poured into a six inch diameter Hermann handsheetapparatus. The forming cylinder was filled to the proper volume and ahandsheet was formed in accordance with TAPPI Method T205.

The single handsheet was pressed on the Hermann sheet press for oneminute at 50 p.s.i. diaphram pressure. Following pressing, the handsheetwas dried for 10 minutes at 240 F., employing a photographers dryer.

As shown in the following table, with parts expressed by weight, aseries of paper handsheet tests was conducted employing gram batches ofcommercial bleached .(grams per square meter). Hence, a low numericalCobb Test rating is highly desirable.

In accordance with Example 1, alum was added to the emulsion in suchamount as to cause the pH to drop to a relatively low acid level (pH 4.5Such addition, however, produced an undesirable high Cobb Test numericalrating of 207. Increasing the amount of alum, in Example 2, in order toobtain a satisfactory Cobb Test rating of 11, resulted, however, infurther raising the acid level to an undesirable pH of 3.8 and alsorequired a relatively large amount of wax emulsion.

In Examples 3 and 4, in order to obtain satisfactory Cobb Test ratingsof 10 and 11, respectively, it was necessary to employ both alum androsin.

On the other hand, as shown by Examples 5 and 6, cmploying small amountsof the cationic coupling agent, and in the absence of either alum orrosin, a satisfactory Cobb Test rating of 13 was obtained in eachinstance.

As hereinbefore indicated, the method for coating surfaces, of thepresent invention, is useful for treatment of a wide variety ofmaterials and substrates and for the manufacture of various articles inwhich coatings of anionic wax emulsions are required. While theinvention has been sulphite pulp. The previously described anionic waxpossessed a molecular weight above about 1 million and exhibited a pHvalue of 1.8 in a 1% aqueous solution.

described with reference to prefered procedures, compositions andcomponents therefor, it will be understood by those skilled in the artthat departures from the preferred embodiments can be efiectively madeand are within the scope of the invention.

I claim:

1. A method for coating a surface, which comprises: initially contactingsaid surface with a minor proportion of the amount of a polyamine saltrequired to precipitate wax particles from an anionic wax emulsion,obtained by reacting a reduced polyacrylarnide with a fatty acid, as acoupling agent; next contacting said treated surface with an anionic waxemulsion; thereafter contacting the resulting mixture with the remainingportion of said coupling agent, whereby wax particles in said emulsionare precipitated onto said surface, and thereafter drying the coatingthus deposited, the minor proportion of the polyamine salt being atleast about 0.1% by weightof the wax emulsion.

2. A method in accordance with claim 1, wherein said coupling agent isemployed in an amount from about 0.1 to about 30%, by weight, based onthe weight of the emulsion solids.

TABLE.-PAPER HANDSHEET TEST RESULTS Sizing treatment 2 Percent Coup-Original Emulling Final Sheet Cobb 3 Freeslurry, sion Rosin Alum agentslurry, wt., test Example Test ness pH solids solids solids solids pHgrams result 1 Anionic wax emulsion and added alum to 4.5 pH 22 5 8 1 4.5 2. 16 207 2-..- Anionic wax emulsion with increased alum to 3.8 pH...-21 5. 8 3 3. 8 2. 14 11 3.. 24 5.8 .7 4.2 2.12 10 4 24 5. 8 7 4. 2 2. 1111 5 22 5. 8 1 5. 6 2. 14 13 6.. 22 5. 8 1 5.6 2. 14 13 1 Used bleachedsulfite pulp; 0.5% beater consistency in distilled water; handsheetsformed in tap water. All sheets dried at 240 F./10 min. then placed inconstant humidity room for 7-10 days before Cobb tests.

3 Solids calculated as a percent of oven dry fiber weight.

As will be seen from the foregoing table, the series of anionic waxemulsions of Examples 1 through 6 were evaluated for Cobb Test results.In this test a relatively high numerical rating denotes a large waterpick-up Table: W t. percen 125/127 A.M.P. paratfin wax 5.0Microcrystalline wax 0.0 Hydrofol acids (CM-C22 fatty organlcaclds) 3.5Diethanolamine Water 3 Cobb test run for 1 min. using cc. of distilledwater on 6 diameter handsheet. Each test result shown is an average offour individual handsheet tests.

4 Coupling agent applied as a 0.04% solution.

7 5 surface comprises paper pulp.

6. A method in accordance with claim 1, wherein said surface comprisescotton cloth.

7. A method in accordance with claim 1, wherein said surface compriseswet process hardboard.

8. A method in accordance with claim 1, wherein said surface comprisesWood.

9. A method in accordance with claim 1, wherein said surface comprisesvegetation.

10. A method in accordance with claim 1, wherein said coupling agentcomprises a polyamine salt obtained by the reaction of an N-alkyltrimethylene diarnine, containing an alkyl group having at least 14carbon atoms, with a fatty acid.

11. A method in accordance with claim 1 wherein said coupling agentcomprises a polyamine salt obtained by reacting a reduced polyacrylamidewith acetic acid and having a molecular weight above about 1 million andexhibiting a pH value of 1.8 in a 1% aqueous solution.

References Cited UNITED STATES PATENTS WILLIAM D. MARTIN, PrimaryExaminer M. R. LUSIGNAN, Assistant Examiner US. Cl. X.R.

